Dual-pressure high-voltage compressed-gas insulated electric circuit breaker

ABSTRACT

Electric high-voltage equipment such as a circuit breaker, includes a chamber in which high voltage parts may be positioned and containing electrically insulating compressed-gas capable of condensation to a liquid under increased pressure and/or lowered temperature. A condensate-collecting container is connected to the chamber to receive the condensed liquid. The chamber operates at high pressure and the container at a lower pressure, causing the condensate to vaporize therein to a gas. This gas is pumped, with increased pressure, from the container back into the chamber where the higher pressure is to be maintained. A float valve controls the discharge of condensate from the high pressure chamber into the low pressure container.

United States Patent [191 Hoffmann DUAL-PRESSURE HIGH-VOLTAGE COMPRESSED-GAS INSULATED ELECTRIC CIRCUIT BREAKER [75] Inventor: Fritz Hoffmann, Reinheim, Germany [73] Assignee: Siemens Aktiengesellschaft,

Munchen, Germany 22 Filed: Jan. 4, 1973 211 Appl. No.: 321,027

[52] US. Cl 200/148 E, 174/11 R, 200/148 B 1 Nov. 5, 1974 Primary Examiner-Robert S. Macon Attorney, Agent, or Firm-l(enyon & Kenyon Reilly Carr & Chapin [57] ABSTRACT Electric high-voltage equipment such as a circuit breaker, includes a chamber in which high voltage parts may be positioned and containing electrically insulating compressed-gas capable of condensation to a liquid under increased pressure and/or lowered temperature. A condensate-collecting container is connected to the chamber to receive the condensed liquid. The chamber operates at high pressure and the container at a lower pressure, causing the condensate to vaporize therein to a gas. This gas is pumped, with increased pressure, from the container back into the chamber where the higher pressure is to be maintained. A float valve controls the discharge of condensate from the high pressure chamber into the low pressure container.

5 Claims, 1 Drawing Figure EDUALPRESSU-RE HIGH-VOLTAGE COMPRESSED-GAS INSULATED ELEC'FRIC CIRCUIT BREAKER BACKGROUND'OF THE INVENTION Metal-cladhigh-voltage electricswitching equipment and the like includes a grounded metal casing which contains a compressed electrically insulating gas such as SE, in the space between the electricallyconducting parts and vthegrou'nded metal casing. Such a gas with DESCRIPTlON-OF THE PRIOR ART One way to-overcome this problem has been to place a thermostatically controlled heater in the casing so that if the ambient temperature dropsand introduces the problem of condensation-within the casing, the heater is turned on to raise the temperature and prevent condensation.

The casing where the gas is confined at .a high pressure suitable for electrical insulation purposes, may be connected with a "lower pressure container interconnecting with the :high pressure casing and from which the gas is drawn, increased in pressure and introduced to the high pressure space, with the heat produced by the compressor-being introduced to the latter to elevate its temperature and prevent further condensation. In the caseofa disconnect switch or circuit ibrea'k-erwhic'h opens and produces large amounts of heat, rapidly raising the pressure in such metal-clad equipment, a pressure sensitive device may operate to power the compresso-r.

All of the above suggestions require thermostatic and pressure controls, extensive plumbing, possibly electrical heating elements and various other equipment, all of which are expensive both to install and to maintain.

SUMMARY OF THE INVENTION One object of the present invention is to provide a simplified means for maintaining the proper pressure on the electrically insulating gas in the chamber enclosing the electrical equipment requiring the insulation, even when condensation of the gas occurs, by a simplifled arrangement or means that does not involve expensive heating of measuring and control elements.

According to the present invention, this object is attained by providing the high pressure chamber when the gas pressure must be maintained, with a bottom or lower part forming a sump in the bottom of which an orifice opens into the low pressure container to which the condensate is introduced for conversion to its gas phase due to the lower pressure there existing. Within this sump a float is positioned which controls a needle valve movable to closed'and opened positions relative to the orifice, the inlet of the latter forming a valve seat. The float has a displacement volume only slightly less than the containing volume of the sumps interior to provide sensitivity, a very small amount of condensate falling to the sump buoying up the float and opening the needle valve from the orifice so that the higher pressure within thec'hamberforces the condensate into the container where the lower pressure exists with consequent vaporization or gasification of the condensate. The float is preferably biased upwardly by an adjustable biasing spring means acting as a float lifting spring, the force of which can be adjusted.

A compressor has its inlet end connected to the low pressure container into which'thesump discharges and its high pressure end connected to the chamber where the gaspressure must be maintained for electrical insulating purposes. In this way a pressure differential is maintainedbetween the container and the chamber. As the condensate discharges into the container upon opening of the needle valve, there is, of course, a refrigerating effect so that the gas insulation, although returned to its gas phase, is cold. However, when the cold gas is sucked by the compressors low pressure side, compressed and returned to the high pressure chamber, the compression of the gas, meaning that work is .put into it, raises its temperature so that relatively warm or hot gas is returned to the chamber from which it condensed.

It follows that with opening of electrical contacts within the chamberwhere the gas insulation must be an effective electrical insulator, the consequent possible pressure rise, or possibly cooling of the gas in this chamber due to a cold ambient temperature in which the equipment is operating, resulting in condensation of the electrical insulating g'as producing an undesirable pressure drop in the chamber, that with the present invention the condensate is discharged through the needle valve into what might be called a condensate container, in its gas phase; this gas possibly being rather cold, is removed by the compressor and compressed with consequent heating and, or course, a pressure increase, and is returned to the chamber where the gas insulation is required, rapidly and without requiring the need for expensive heating, measuring and control ele ments.

If it is considered undesirable for the compressor to operate continuously, relatively inexpensive means may be provided for detecting a change in the pressure differential between the chamber and the container, such means then causing the compressor to operate so long as the pressure differential measurement indicates the need for such operation. Here it is to be assumed that the compressor is powered by an electric motor.

BRIEF DESCRIPTION OF THE DRAWlNG A preferred embodiment of the present invention is illustrated by the accompanying drawing wherein the single FIGURE schematically shows the bottom of the chamber containing the electrical equipment (not shown) with the low pressure container and the interconnecting sump and float valve arrangement shown in vertical section.

DESCRIPTION OFTHE PREFERRED EMBODIMENT Having reference to the above drawing, the high pressure chamber 1 which must connect with the low pressure container 2 has its bottom 3 shaped to provide a sump enclosing an interior space 4 into which any possibly condensed gas falls, it being understood that the chamber 1 contains the compressed gas insulation which is capable of condensing in the case of a pressure increase due to the electrical arcing or other action of 4 has almost, but not quite, the containing volume which can be related to the displacement volume of the float 6. The sides and bottom of the float 6 substantially coincide in contour to that of the space 4 defined by the sump formed in the bottom 3. j

The spring suspends the float-actuated needle valve 7 which is in the form of a long rod extending to above the upper part of the spring and engaging with the latter via adjustment nuts 7a. The orifice in the bottom of the sumpdefining the space 4 is shown at 8, the upper portion of this orifice being normally closed by the tip of the needle valve 7. The orifice is made with a substantial length.

The compressor which draws the gas from the container 2 is shown at with its output connecting with the chamber space 1 where the gas insulating pressure must be maintained. This compressor draws from the container 2 via a suitable fluid filter 9.

in operation, .condensate formed in the chamber 1 flows into the sump space 4 and lifts the float 6 with consequent lifting of the needle valve 7, the liquified gas discharging through the orifice 8 into the lower pressure container 2 and converting to its gas phase. This gas is drawn by the compressor 10 and forced under the necessary higher pressure into the chamber 1 so that the pressure in the latter is maintained at the necessary pressure value.

By adjusting of the lifting bias of the compression spring 5, together with the face that the float 6 almost, but not quite, completely fills the space 4, sensitive response of the needle valve 7 is obtained.

Although not shown, pressure differential actuated .4 means may be used jto start and stop the operation of the compressor 10 assuming that it is electrically powered. In other words, automatic means (not shown) may be provided for maintaining a predetermined pressure differential between the high pressure chamber 1 and the low pressure container 2.

What is claimed is: v

1. Electric high-voltage equipment including a chamber containing electrically insulating'compressed gas which condenses to a liquid under increased pressure and/or lowered temperature, a condensate collecting container positioned and connected with the chamber to receive the condensed liquid therefrom and which is maintained at a reduced pressure returning the condensate to gas, and a compressor connected to this container to remove the gas therefrom and force it into the chamber to maintain in the latter the electrical insulation provided by the compressed gas; wherein the improvement comprises means for forming a fluid connection between the container and the chamber and which is responsive to the production of condensate in the latter to open the interconnection and which otherwise closes the interconnection.

2. The equipment of claim 1 in which said means is a sump in the bottom of the said chamber for receiving the condensate, the sump having an orifice in its bottom forming a valve seat and a needle valve normally closing this orifice, a float connected to the needle valve lifting the latter when condensate collects in the sump. v

3. The equipment of claim 2 in which thesump and float are relatively proportioned so that the displacement volume of the latter is only slightly less than the containing volume of the former.

4. The equipment of claim 3 in which the float has an upward biasing means. I

5. The equipment of claim 4 in which the biasing means is adjustable. 

1. Electric high-voltage equipment including a chamber containing electrically insulating compressed gas which condenses to a liquid under increased pressure and/or lowered temperature, a condensate collecting container positioned and connected with the chamber to receive the condensed liquid therefrom and which is maintained at a reduced pressure returning the condensate to gas, and a compressor connected to this container to remove the gas therefrom and force it into the chamber to maintain in the latter the electrical insulation provided by the compressed gas; wherein the improvement comprises means for forming a fluid connection between the container and the chamber and which is responsive to the production of condensate in the latter to open the interconnection and which otherwise closes the interconnection.
 2. The equipment of claim 1 in which said means is a sump in the bottom of the said chamber for receiving the condensate, the sump having an orifice in its bottom forming a valve seat and a needle valve normally closing this orifice, a float connected to the needle valve lifting the latter when condensate collects in the sump.
 3. The equipment of claim 2 in which the sump and float are relatively proportioned so that the displacement volume of the latter is only slightly less than the containing volume of the former.
 4. The equipment of claim 3 in which the float has an upward biasing means.
 5. The equipment of claim 4 in which the biasing means is adjustable. 